When the Proposition 19 marijuana legalization initiative qualified for the ballot in the November election, its passage seemed almost a foregone conclusion.

Tax the approximately $12 billion pot industry in this state and you could collect $1.4billion toward solving the state’s budget deficit, not to mention helping out cash-strapped local governments.

You would also take hundreds, maybe thousands, of law enforcement officers off the drug beat and allow them to go after “real criminals,” said supporters of legalization.

Since many surveys show that well over 50percent of adult Californians have puffed a reefer at some time in their lives, you would think passage would be a snap.

But the polls don’t all look that way. In fact, indications are there’s a strong possibility this proposition could fail, just like a similar one did 38 years ago, in 1972.

The usually reliable Field Poll last month found that 48 percent of likely voters opposed legalization, while 44 percent were in favor. That seems like a narrow margin, but ballot propositions that trail several months before an election usually lose. Other recent surveys using live questioners yielded similar results.

And yet, in three automated polls taken at about the same times with questions asked robotically, the measure led by as much as 15percent. So voters may be lying to the live operators out of some sense of shame.

A six-month study by the nonpartisan Santa Monica-based Rand Drug Policy Research Center, released at almost the same time as the poll results, gives many clues about why they might feel shame about legalizing pot, even if they eventually vote for it.

The number of pot smokers in California would rise significantly, the study concluded, but no one knows exactly how much because no one knows either what the tax might be on an ounce of cannabis or the level of tax evasion that might ensue.

(Another unknown: Would Republicans who have taken a “no-new-taxes” pledge make an exception for a pot levy?)

For sure, the report says, marijuana prices would drop sharply, just like the price of liquor after Prohibition. An 80 percent drop is a strong possibility, the report said.

This, too, would have tax implications. The estimates of about $1.4 billion in tax revenues after legalization are based on current prices, which often top $300 per ounce.

One more factor with probable heavy tax implications: The proposed new law would allow cannabis cultivation by anyone. It’s unclear whether home gardens could be taxed, or how a tax collector might learn about any individual garden. Also unclear: What drug-cartel operators of the many indoor hydroponic farms and large marijuana gardens in California’s national forests might do.

All this, of course, raises the real question about legalization: What damage could it do? This country, as initiative sponsors note, already has more pot smokers than any other, despite current enforcement efforts.

While Proposition 19 specifically allows governments to retain bans on bringing pot to schools or peddling it there and lets them keep laws against driving under its influence, there’s nothing to prevent the kind of general malaise of which the Harvard University Mental Health Letter warned in its April issue.

“The psychiatric risks are well documented,” the journal said. “They include addiction, anxiety and psychosis.”

Just what California needs: More anxious, psychotic pot smokers.

Nobody is quite sure why, but these kinds of fears and questions may be more prevalent among minority voters than whites. The Field survey found that while white likely voters support the measure, it is heavily opposed by Asians, Latinos and African-Americans. Could this be because the drug culture is viewed least romantically by those it damages most?

Field also found women oppose legalization by a 9 percent margin while males are evenly divided.

Did lying by voters who fear being exposed as pro-drug somehow influence the live poll findings? Maybe, but Field poll director Mark DiCamillo has often talked about how he and other pollsters compensate for responders’ inevitable lies. But this is no ordinary issue: The results of automated polls like those run by Survey USA suggest pot may spur far more than the normal amount of prevarication.

The pot initiative is also hurt by its own vagueness: It leaves all regulation up to cities and counties while spelling out very few details. The past is full of inequitable laws enacted to “clarify” what the voters meant after they passed initiatives like the 1978 Proposition 13 property tax cuts and the 1986 Proposition 65 clean water initiative.

All of which makes the fate of Proposition 19 as uncertain as any proposition’s ever has been. For sure, if this one loses, it will not be by nearly as large a margin as the 2-1 defeat suffered by the state’s previous attempt at legalizing marijuana.